Acid-reclaiming apparatus for sulfite-mills.



e. s. WITHAM, SR. I JJ. MCEWEN.

ACID RECLAIMING APPARATUS FO'R SULFITE MILLS.

APPLICATION FILED DEC.. 1I 1915.

Patented May 16, 1916.

UNITED s'rArrEs .PATENT onirica.4

GEORGE s. w1THAM,`sn.,'oF-i1UDsoN rALis, A`Nn JAMES, J. MCEWEN, oF FORT EDWARD,

-NEW YORK.; i

AQID-BECLAIMING APPARATUS Fon sULFITE-MILLS.

To ZZ whom may yconcern.' .Y

Be it known that we, GEORGES. V'ITHAM. Sr., of Hudson Fallsyin thecounty of 'asliington and Stat'eof New York. and JAMES J. MrcEwEX, of Fort Edward. in the county of'll'ashington and State ofXew York, both 5 citizens of thenit'ed States. have invented certain new andl useful Improvements in Acid-Reclaiming Apparatus for Sulite- Mills. of which the following a specification. 1` Y i A Thls invention relates to certain improvements in apparatus employed for the manufacture of wood Vpulp bythe well known sultite process. in which the wood in suitably' sub-divided form is cooked" in adigelster' while mixed with sulfite liqiloialnder:heatand pressure produced by steam admltted tothe digester.` Inpsuch a system it is Yusual to relieve Ythe pressure in the digestelat frequent intervals in order to reduce it and to admit more of the heating agent. and it is the practice afterthe cooking operation is complete to pass4 the contents ofthe digester to' whatl is called a blow-pit.

Qrdinarily the gases and liquor discharged from the top of the digester when relieving it of pressure are wasted. although various ways of utilizing or reclaiming tliemhave been proposed. and it is customary 'te discharge the liquor passing with the treated flberfrom the d igester to the blow-pit. and

to entirely discard said liquor. i

According to our-invention. 'we provide means whereby all the gases and' liquor' withdrawn :from the digester through the relief valves isvr saved and combined with the 'sulite liquor for charging the digester. ve also :provide meanswhereby the liquor withdrawn from the digester with thecooked fiber is combined with vthe fresh suliite liqnor while the latter issbeing formed for use in the digester. f

In carrying out our invention. we pro` vide means. preferably in the form of a vertical tube or tower. for combining@ sulfur dioxid (SOL.) with an alkaline liqubr such as lim'e 4water. and we provide means for mixing the sulfte liquor thus formed with the gases andfliqor vwithdrawn from the top of the digester and also with the' liquor withdrawn' from the bottom thereof in such manner as to provide a sulte liquonsuitable for use in the digestger.

)Iore specifically the preferred apparatus Specification of Letters Patent.

comprises a towe' containing lime stone and to which snlfu'r dioxidirom a sulfur burner is admitted near the bottom and to which liquid, such as water, is supplied at' the top.

.The acid liquor forme-d is conyeyedfto a tan-k .which also receives the gas 'withdrawn from thetop ofthe digester, and from this f which snppliesthe digester with the enrlched-sulite liquor.

Vixen the dige'ster is blown or emptied, its contents pass to the blowgpit and after most ofthe fiber ha's'been separated'from the liquor the glatter is conveyed to an apparatus whlch separates the relnalning fibers troni the liquor, the Vformer being carried away by suitable trucks and the latter being conveyed toa tank above the tower. from which tank the liquor descends 'into the tower and passes downwardly through the limestone therein., The tank is connectedy vwith the tower by a conduit wlnclrconveys Pafenteaarayie, 1916. Application lea ecember 11,1915. serial No. 66,391. Y y

the unabsorbed gases which reach tliie top of t'l1e' tov\"er tothetank above it. where they are to a large extenabsorbed by the liquor therein. In this way we are enabled to use a relatively short tower as the gas which first enters the bottom of the tower is, to a large extent. absorbed before reaching the top thereof and such gaseszas do reach the" upper' end of the tower are conveyed to the tower supplyY tankandy are absorbed by the liquid therein` and descend with such liquid.

into the tower land act upon 'the lime stone therein. In Vthis way practically lall of the gases entering the tower ai'e'completely absorbed. l

ve provide the several tanks with means of novel construction which cause the gases and liquors withdrawn from the dige-stento '.be thoroughly intermingled in such manner 'that the gases are thoroughly inlxed and abno loss of gas 1n the vsol-bed and there is process. .n I

In our reclaiming system the gases are made to traverse gas-tight tanksl and conduits so that nogases or vapors are lost but are all absorbed and enter intocombinaf tionwith other constituents of the liquor. while the liquor passing from both thefftop and bottoniA of the digester is conveyedkitoj combined with the sulfite liquor for charg' mg the digester. In this way there 1s no f loss of the chemical agents employed as they are all reclaimed and used in the process so that a very large saving in the consumption of sulfur is effected.

Experience has demonstrated that by the use of our apparatus the quality of the pulp is improved and there is avery large saving in the cost of operation. Usually sulfite mills as at present operated consume from 275 to 350 pounds of sulfur to each ton of sulite, while we :only use from :200 to'215 pounds of sulfur to the ton.

In the accompanying drawings, we have shown our acid reclaiming system applied: to a single digester, but it will `be understood that it may be embodied in a plant or system in which al plurality of digesters are Figure 1 shows diagraminatically .apparatus embodying our invention. Fig. 2 is a detail view on an enlarged scale of parts of the tower and the tower supply tank.`

Fig. 3 shows a section on the line. 3 3. of

l `Fig. l, and illustrates on an enlargedxscale one of the mixers which we employ.

The digester A is, as usual, equipped with a removable top a., a Irelieit pipe a or liquor and a relief vpipe f1.2 for gas. Steam may be admitted at a3 as usual, and the digester may be emptied through "a pipe B leading to a blow-pit C'The' digester is supplied with sulfite liquor througha pipe D.

E indicates a tower 'for containing limestone. Sulfur dioxid from aJ sulfurburner is admitted to the lower portion of the tower througha pipe e. This tower may be of usual construction. but is not so high as those ordinarily used. Instead of making the tower 120 feet high as vis often the case,l

we preferably make it half as high, say feet. On, top of the tower there is a tank F to'which watermay be supplied in any suitable way. This tank is closed gas-tight and communicates with lthe tower through a pipe f provided with an enlarged perforated discharge end f' .and with a lopped portion f2` providing a column forming a trap or seal. It will be observed that the pipe]c extends to near the'top of the tank and the liquid overflows through this pipe and passes down through the limestone in the tower. The sulfite llquor thus formed passes through pipe vgtoI a tank G.' Any` gas which after. lhaving passed upwardly through the tower is unabsorbedby the liquid. passes through the pipes H to the lower portion of the tank F and is practically all absorbed by the liquid therein.

live preferably employthree mixing tanks J, K. L. These are closed at the top, being gas-tight throughout. The gas relief pipe a? extends to the tanks J and la andis provided into the several tanks, as

.with branches j,-c extending the'bottom however, that itis not absolutely necessary that the gas and liquor should pass into all the tanks mentioned. We 'prefer to havey the gas pass into the tank J and the liquor into the tank K, but improved results are obtained by-having the gas and liquor pass indicatedin the drawings.

In order to obtain the best results itis importantethat the gases or bubbles admitted to the mixing tanks should be delivered thereto in'a` sub-divided condition in order that they may be completelyabsorbed,.and

4for this purpose we employ a mixer 'M which is preferably constructed in the manner inand 'z, shown in the/drawings may `vided with such a mixer and we may also provide the gas pipe a2 with a branch pipe Z extending into the tank L and this pipe may also be provided with 'a mixer.

-by this arrangement-thegas in the form of bubbles is made to enter the tank atA different radial distances from the central axis of the tank. The mixer is stationary, but

yals the acidor gas leaves'the arms m a circular motion is given tofit and as the-arms are ofvditferent lengths la pressure is exerted' at a different radial distance 4from Vthe cendicated'in Fig. v3. Each of the pipes j, pro- Such j 'mixen as shown, comprises a series of holtral vertical axis of the supplypipe'. -This n produces a whirling motion of the hquor which is found to be .most eflicient the process..- The liquor enteringthe vJ loverflows through apipen to the tank'K and from the tank( K the liquor passes through aiconnection n' to the tank L which suplplies the digester. vVhen the apparatus is properly working the gases vare completely absorbed, but as a precaution we provide a pipe O, connecting with the tanks J, K and L and `leading to the lower portion of the tower E. toconvey thereto any gases that may not be absorbed in the tanksl The acid liquor which'passes from the bottom of the tower is first received by a tank G. rom

which itis taken to a pump G andielevated through a pipe g. to the tank d and in the 'tanks J, K and L it mise.- with and is enof the blow-pit may be tr'nsferred'at suit-` able intervals to a box ortroughc by way of a gate c.- Most of the `fibers are here y separated from the liquor and from this Atrou-gh c tlie remaining ibers and liquor are elevated b v means of rator Q which may struction. 'passes b v receptacle, such as a t truck R. The liquor thus separated from the fiber is conveyed by a pumpP to a sepabe of any suitable cona pipe S to the tank F where -it is mixed t with tlie liquor' derstood that` this tank in said tank. and passed through the system in-the manner before described. In orderto promote the mixing of gas with'the liquor in the tank F `we employa vacuum pump-T, of well known construction, which is connected by a pipe t with the ltop of` the tank F. Itwill be unbut is connected with the vacuum pump for the purpose of producing such relief of vpressure as to cause t-legasesto readily ascend in the tower and iisieie tank and convey off the unabsorbed ga 'Thepipe f serves to convey liquor from the tank F ytothe tower.

The loop f2 in said pipe provides a liquid column which forms a trap or seal high enough to overcome any partial vacuum produced in the tank and thus prevent any 'lates For the most gas from passing from the tower through said pipe to the tank. T he partial vacuum produced in the tank F prevents liquor from rising in the pipes H and causes gas to' be drawn through saidpipes from the tower to the tank.

'It will be understood that the valve of the gas pipe a2 is closedwhile the digester is being relieved ofliquor. When the liquor h as allbeen blownoff the valve of the liquor pipe is closed and the.

pipe opened to relieve the pressure and permit the remaining gases to pass to the mixing tanks. Some of the apparatus is merely illustrative in a conventional way'but the details I of construction are well known to those skilled in `the art to which this invention repart our invention is not limited to any specific form of apparatus but consists in subject matter hereinafter specified. I

It will be understood that the lime required for the. suliite liquor is derived from thelime stone contained in the tower but if and. liquor .withdrawn connected with llivered -to the tank F. also a washing tank and water is supplied From the separator the fiber Y means of a-chute Q to any suitable is closed gas-tight liquor -to the digester,

valve of the gas 'mills comprising forA instance, may be added to the pump box ditions are, however, Liquor 1s taken from the pump box andv de- The blow pit C is to this tank for the purpose of washing the fibers by a hose. -The supply is not fixed but is used when required. n

`The Separator extracts all solid matter from the liquor before said liquor passes to the lime tower. Fresh water is added tothe 4pump box as often as required to compensate forthe natural shrinkage in continuous operation. The fresh watei' added is suiiicient .to prevent the liquor from becoming thick or mtensified rl`h-is operation can be carried on for an indefinite time. Thatever gums pass from theseparator to the lime tower are deposited inthe lime tower as a residue. i We claim as our inventionzi 1. A reclaiming apparatus for sullite mills. comprising a 'tower for mixing sulfur dioxid., containing gases with an alkali, a mixing tank to. which the acid liquor is conthe separator Q. Such. ad-A rarely necessary.'

veyed from said tower. a digester, means for conveying the digester to said mixing tank. means for thoroughly inixingsaid last mentioned gases with the liquor, and means' for conveying the enriched liquor tothe digester.

2. A reclaiming. apparatus `for Sulite mills, comprising means for mixing' sulfur dioxid containing gases with an alkali, a closed gas-tight' mixing tankto which the acid liquoris conveyed from saidl mixing means.v a digester; means for conveying gases withdrawn from the digester to said mixing' tank, means for thoroughly intermingling said last mentioned gases with the liquor, and means for conveying the enriched means for discharge ingjthe contents of the digester, means for separating digester the liquid therein and means for conveying such separated liquid tothe means for mixing sulfur dioxid with the alkali.

3. A reclaiming apparatus for sulte means lfor mixing sulfur Acontaining gases gases'and liquor withdrawn fromfrom .the fibers discharged by the dioxid containingl gases with an alkali, a

mixing tank to which the acid liquor is-conveyed from said mixing means, a digester,'

means for conveying gases withdrawn from the top of the d igester to said imxing tank,

a mixer through which said gases are delivered tothe liquor in themixing tankand which comprises a series of'radially curved z v hollow arms lfof different lengths.'

. 4. In a reclaiming apparatus-for sullte mills a mimng tank whereggaseswithdrawn from a digester are mixed with s'ulte liquor and which is provided with aA mixer for the 4necessary lime, in the form ofmiikof'lime,

gases withdrawn from this digest'er consisting of a series of Vradially curved hollow' Y arms of dierent le'ngths.

5. In a reclaiming apparatus for sulte mills, a tower. means for supplying sulfur dioxid containing gases to the lower portion thereof, a -supply tank abovethe tower and connected therewith. means torv producing a.

partial vacuum in the tank. connections between the upper portion of the tower and the lower portion of the tank for conveying y gases from the top of the tower to the tank,

a mixing tank to which the acid liquor is conveyed from said tower. a digester. means for conveying gases and' liquor withdrawn from thedigester to said mixing tank. niean= for thoroughly mixing said last-mentioned gases with'the liqiior. means for -conveying the enriched liquor to the di'gester, and

` means for conveying gases'l not absorbed in discharging the contents of the digester,

means for separating from the fibers disv' charged by the digester the liquid therein. and means for. conveying such separated liquid to the tank above the tower.

T. A reclaiming apparatus for sulfite mills'. comprising means' for mixing sulfur dioxid containing gases with an alkali, a series of mixing tanks. meansl for conveying the sulfur treated alkaline liquor to each of (said mixing tanks. a digester. means for conveying gases and liquor withdrawn from the digester to'said mixing tanks, a storage tank to .which the enriched liquor 1s delivered,

and connections between said storage tank and the digester.

8. A reclaiming apparatus 'for sulte mills. comprising a tower. means for Iadmitting sulfur dioxid containing gases to the lower portion thereof. a gas-tight tank above the tower for containing liquor. means for conveying said liquor 'to the upper portion of the tower. means for producing a partial vacuum in said tank. connections between the upper portion of the tower and the lower portion of the tank'to convey'gas from the tower to the tank. a digester. means for separating from the fibers discharged by the digester liquor inixedtherewith, means for conveying such separatedi liquor to the tower-supply tank. mixing apparatus. means for conveying to said mixing apparatus acid liquor from the tower. and means for conveying to said mixing apparatus gases and liquor "withdrawn from the top of the dig'ester.

'In testimony whereof. we have hereunto subscribed our names.

GEORGE s. wrrnxii, sa. Jamas J. iicnwnx.

Witnesses GEORGE G. Dt'nxx'i,

' GEORGE il Lrox. 

